The electrical grid connecting America's power plants, transmission lines and substations to homes, businesses, and factories operates almost entirely within the realm of high voltage alternating current (AC). Yet an increasing fraction of devices found in those buildings actually operate on low voltage direct current (DC). These devices include, but are not limited to, digital displays, remote controls, touch-sensitive controls, transmitters, receivers, timers, light emitting diodes (LEDs), audio amplifiers, microprocessors, and virtually all products utilizing rechargeable batteries. A challenge of the primary power distribution infrastructure in modern commercial buildings is the need for conversion of power from high voltage, generally 110-230 volts AC, to low voltage, generally 3-24 volts DC.
Currently, conversions from high voltage to low voltage are accomplished via a device commonly referred to as an AC/DC “transformer” or “power adapter.” The present practice in the low voltage device industry, which today primarily includes components from the solid-state electronics device industry, is to design device specific, i.e., dedicated, AC/DC transformers, since much is known about the specifics of a single device. It is estimated that there are more than 3.1 billion devices in use across the United States of America, which utilize an AC/DC transformer. A typical AC/DC transformer is illustrated in FIG. 1. The AC/DC transformer shown in FIG. 1 includes an AC input 10, a transformer 15, a rectifier 20, and a linear regulator 25 arranged to provide a DC output 30. The operation of the AC/DC transformer is well-known in the art.
It is widely known that such transformer/adapters vary significantly in efficiency. On average, about 50 to 60% of the power entering the high voltage AC input side of these transformers typically leaves as low voltage power on the DC output side. The remainder is consumed as waste heat. Therefore, improving the raw electricity consumption efficiency of conventional AC/DC transformers has the potential to dramatically reduce energy costs.
Load variation, or the amount of power actually needed at any given point in time versus any other point in time, is generally considered the most important factor in determining raw power consumption efficiency. Unfortunately, conventional low cost AC/DC transformers are designed to maximize their efficiency given a specific expected load or range of loads, thus producing efficiencies which are statistically highly variable.
A factor to be considered, when distributing power in the building interior, is the U.S. National Electrical Code (NEC) Class II and Class III power requirements for low voltage direct current (LVDC) circuits. In this regard, the NEC puts significant limitation on the total power available for devices attached to any one conductive segment as described therein. More specifically, Class II and Class III requirements restrict the connected load in an individual circuit to a maximum of 100 Volt-Amps. For example, in a circuit that is designed to operate nominally at 24 volts direct current (VDC), the connected current would be limited to approximately 4 amps (i.e., 100 Volt-Amps divided by 24 VDC=4.167 amps). In other words, loads exceeding 4 amps must be powered by at least two electrically isolated power sources, none of which individually exceeds 4 amps. Such load management, including real-time monitoring, is not sufficiently accommodated in current LVDC power distribution systems.
For the above reasons, there is a need to actively adjust the “grouping” of such potentially variant loads for the purposes of averaging the power load to be statistically less variable with respect to changing demand. Additionally, there is a need for a power management system in the building interior, including, but not limited to an individual ceiling environment, which can limit the amount of power distributed on any given “branch” of the grid network, such that the grid network complies with the full requirements of the NEC Class II or Class III.